The advent of rigid permanent magnets has afforded near revolutionary progress in magnetic technology with substantial advancements in magnetic field strength, structural compactness and design simplicity. The term “rigid” as used in this context is defined as the constancy of magnetization, M, that these materials can afford. Thus, a rigid magnet is one whose magnetization, M, is not affected by demagnetizing fields engendered by the geometry of the structure into which the magnet is placed. The use of a rigid permanent magnets with a constant magnetization, M, that is unaffected by the demagnetizing influences of the surrounding structure permits arranging an array of permanent magnets so that the surrounding structure's magnetic poles work to the designer's best advantage without demagnetizing the magnets. Accordingly, the individual magnetic fields of rigid permanent magnets may be summed in order to compute their total magnetic effect when the rigid permanent magnets are correctly aligned.
To better understand constant magnetization M magnetic structures it is useful to consider the relationship between magnetic remanence, B, magnetic field, H, and magnetization M. When assembling a magnetic structure such as a magic ring, the conditions of rigidity of magnetization {right arrow over (M)} and the satisfaction of various boundary conditions leads the values of magnetic remanence {right arrow over (B)} and magnetic field {right arrow over (H)} to be held constant within any single segment. The three quantities are related by the fundamental equation:{right arrow over (B)}={right arrow over (H)}+{right arrow over (M)}where magnetic remanence {right arrow over (B)} magnetic field {right arrow over (H)} and magnetization {right arrow over (M)} are expressed in units of magnetic flux density, such as Heavyside units. In a conventional permanent magnet structure composed of rigid magnetic segments, {right arrow over (M)} is the fixed quantity while {right arrow over (B)} and {right arrow over (H)} are the variable quantities that adjust themselves to satisfy the boundary conditions of Maxwell's equations. FIGS. 1 and 2 illustrate one such implementation where the rigid permanent magnet segments are assembled into a magic ring. FIG. 1 depicts a group of wedge-shaped magic ring segments 11 with their respective individual magnetic fields, as represented by small arrows 12-14, and an overall magnetization direction 15 in the midst of the segments 11. FIG. 2 depicts the FIG. 1 group of wedge-shaped magic ring segments 11 assembled into a magic ring 20 wherein the individual magnetic fields 12-14 of the magic ring segments 11 provide a composite magnetic field represented by large arrow 21 in the interior working space to provide a constant magnetization, M. The same configuration would also result if it was possible to hold either of the other two quantities, i.e. {right arrow over (B)} or {right arrow over (H)}, to a fixed value. In that case, {right arrow over (M)} and the other unfixed member of the {right arrow over (M)}, {right arrow over (B)} and {right arrow over (H)} triad would then adjust themselves.
Although it is possible to fix magnetic remanence or magnetic field, B, constant in such magnetic structures, up until now the magnetic fields generated in rigid permanent magnetic structures using conventional materials, such as SmCo, NdFe and PtCo were generally about 20,000-30,000 Gauss. The limitations of rigid permanent magnetic structures fabricated from conventional materials have created a longstanding need for fixed remanence B permanent magnetic structures with stronger magnetic fields. Additionally, a fixed remanence B permanent magnetic structure can also give rise to a higher magnetization, M. Finally, it would also be very desirable to construct magnetic structures having a fixed magnetic remanence, {right arrow over (B)}, in the interior working space, an increased magnetic field and a higher magnetization, M, but currently this cannot be done easily due to the limitations of conventional magnetic materials.
The possibility of holding {right arrow over (B)} to a fixed value along with a constant magnetization M can now be realized through the use of high temperature superconductive segments that exhibit an unusually high capacity for trapped magnetic flux. Previously unavailable high temperature superconductive magnetic segments now make it possible to configure a permanent magnetic structure composed of rigid particles in such a way that {right arrow over (B)} can is fixed at different local values in such a way that magnetization {right arrow over (M)} remains constant over a larger segment as a whole, without suffering from the drawbacks, shortcomings and limitations of constant magnetization M structures fabricated with conventional materials.